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Discussion Starter · #1 ·
Can anyone post up possible HP gains from boring out and adding in forged pistons-rods-balanced shaft on their RS/GS and if it will weaken the block's structural integrity to run Boost or N20 on?
 

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15 WHP, maybe. You're not going to gain anything by going 20 or 40 over and anything more starts to get iffy.
 

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Unless you were changing the compression ratio I doubt you would see any major power gains or losses just from changing the pistons/rods.

Overboring won't affect the structural integrity. In the typical overbore you're usually talking about taking .020" to .040" off. To put it in visual terms .5mm to 1mm.

Eliminating the balance shafts should free up some horsepower but it comes at a cost. Unless you have your rotating assembly balanced, you will have a lot more vibration coming from your engine.

I recommend you become good friends with the Search button. I gave you the short answers because these questions have been covered before. If you are having trouble finding technical answers on here then I suggest checking out Evolutionm.net. Chances are you will find a precise answer within 20 minutes of searching.
 

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15 WHP, maybe. You're not going to gain anything by going 20 or 40 over and anything more starts to get iffy.
Not even. An overbore of .040 on a 2.0L block barely even gives you 2.05L. There are no gains to be seen from an overbore. The only reason to overbore an import motor is make sure that you have a perfect cylinder wall.
 

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Can anyone post up possible HP gains from boring out and adding in forged pistons-rods-balanced shaft on their RS/GS and if it will weaken the block's structural integrity to run Boost or N20 on?
if installed and setup proberly you can install an 75 shot pretty safely
 

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Not even. An overbore of .040 on a 2.0L block barely even gives you 2.05L. There are no gains to be seen from an overbore. The only reason to overbore an import motor is make sure that you have a perfect cylinder wall.
Yeah, I said there are hardly any gains from the overbore. The potential 15 WHP would come from the balance shaft delete and lightening/balancing of the rotating assembly. He mentioned all of that in his post.
 

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I know he didn't say it right so I understand why you miss read him. :fawk: He states forged pistons and forged rods and a balanced shaft which I'm assuming to be a balanced crank. Doesn't mention a balance shaft removal which after seeing what it would do to our race car engines this year I wouldn't recommend anyways.

Eliminating the balance shaft is the only thing that would get him a little more power. The reduced weight in rotational mass doesn't create more power, it allows the engine to rev freer only.
 

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I know he didn't say it right so I understand why you miss read him. :fawk: He states forged pistons and forged rods and a balanced shaft which I'm assuming to be a balanced crank. Doesn't mention a balance shaft removal which after seeing what it would do to our race car engines this year I wouldn't recommend anyways.

Eliminating the balance shaft is the only thing that would get him a little more power. The reduced weight in rotational mass doesn't create more power, it allows the engine to rev freer only.
Removing the balance shafts is something that has always puzzled me since entering the import world. :scratch:

I had been taught years ago that race engines often added balance shafts to reduce vibration allowing them to rev higher (full race only engines, such as those used in Indy cars, not production street engines that have been modified)...I understand the benefits from reducing the rotational mass, but at what cost? I guess that's what you guys found out the hard way this year though, if I read your post right...:ugh2:
 

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There are two purposes of balance shafts in a 4 cylinder engine such as the 4G6x. The first is to reduce vibrations at certain RPM points. The second is to make sure that the oil pump remains true. The front case contains the oil pump and it consists of two internal gears. The one gear is connected to a sprocket that the timing belt rides on. This is what powers the oil pump and is why oil pressure is directly related to engine speed. The second gear is attached to a balance shaft that rides on a bearing inside the block. The bearing inside the block helps to keep the gear tracking smoothly without vibrating or wobbling which helps to preserve the oil pump from premature wear.

When you eliminate the balance shafts, you normally use a stubby shaft that eliminates the second gear in the oil pump from having the support of the bearing. This stubby shaft is now free to wobble which causes premature wear on the shaft that connects the first gear to the sprocket on the timing belt. I don't even want to count how many pump issues or failures I've witnessed this year. We literally lost an opportunity to beat AMS Chicago at Summit Point Redline Time Attack because of this.

There is a work around for this which AMS Chicago does sell on their website. The funny thing is that Nick at DTM created the exact thing AMS did three years ago but the majority said it was worthless and not necessary. That was back in the drag racing days with EVOs. Road racing is a complete new ballgame and it certainly does help in that regard. We have produced a bunch of these modified balance shafts and they are way superior to a stubby shaft. They will be on my website for sale soon at a price that is less than AMS's. ;)
 
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There are two purposes of balance shafts in a 4 cylinder engine such as the 4G6x. The first is to reduce vibrations at certain RPM points. The second is to make sure that the oil pump remains true. The front case contains the oil pump and it consists of two internal gears. The one gear is connected to a sprocket that the timing belt rides on. This is what powers the oil pump and is why oil pressure is directly related to engine speed. The second gear is attached to a balance shaft that rides on a bearing inside the block. The bearing inside the block helps to keep the gear tracking smoothly without vibrating or wobbling which helps to preserve the oil pump from premature wear.

When you eliminate the balance shafts, you normally use a stubby shaft that eliminates the second gear in the oil pump from having the support of the bearing. This stubby shaft is now free to wobble which causes premature wear on the shaft that connects the first gear to the sprocket on the timing belt. I don't even want to count how many pump issues or failures I've witnessed this year. We literally lost an opportunity to beat AMS Chicago at Summit Point Redline Time Attack because of this.

There is a work around for this which AMS Chicago does sell on their website. The funny thing is that Nick at DTM created the exact thing AMS did three years ago but the majority said it was worthless and not necessary. That was back in the drag racing days with EVOs. Road racing is a complete new ballgame and it certainly does help in that regard. We have produced a bunch of these modified balance shafts and they are way superior to a stubby shaft. They will be on my website for sale soon at a price that is less than AMS's. ;)
Sweet...good info on the oil pump gear issue...I wasn't aware of that. I'll be looking forward to a price on your modified balance shafts, although it won't be for a while since an engine build is going to have to be put off until the wife and I buy a house sometime next year.
 

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OK, so I really need some clarification on the whole balance shaft elimination thing. It frees up some hp by reducing the rotational mass right?

Now you say it can wobble... so if I get my stock balance shaft turned down it will be more stable?

And, if I get my whole pistons/rods/crank balanced and then use the balance shaft, is that going to "unblanace" it since its already balanced?
 

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OK, so I really need some clarification on the whole balance shaft elimination thing. It frees up some hp by reducing the rotational mass right?
Yes. :bigthumb:

Now you say it can wobble... so if I get my stock balance shaft turned down it will be more stable?
Pharm is going to have to elaborate on this one for you...I'm not sure if he turns the stock balance shaft down, or if it's an entirely new unit...I'd be a little leary on the average machine shop doing this though...while they could effectively machine one to whatever specs you gave them, I'd want someone who has done the R&D with regards to what the optimum diameter, etc. should be to perform the work...:ugh2:

And, if I get my whole pistons/rods/crank balanced and then use the balance shaft, is that going to "unblanace" it since its already balanced?
Again, I'm going to let someone else elaborate more here since I haven't had one of our engines balanced before. As far as basic balancing principles though, you typically want the entire rotating assembly to be available at the time of balancing (to include the flywheel or flexplate, harmonic balancer, etc. Since we have balance shafts as well, I don't know if it would negate their need (with regards to vibration control, not the oil pump issue discussed before), and I'm not sure if they should be given to the balance shop as well (since they are belt driven off the crank and not directly attached to it...:ugh2:
 

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Discussion Starter · #14 ·
Yeah, this is an expensive operation but it is already finished on my car because for some reason my piston over-extended and started knocking lightly on my block and eventually it got harder and harder, ran itself low on oil, scored the piston walls, and with 98k miles on it, i'm not going to complain about replacing all of that so my car should be back togather by the weekend and i can test it out. i plan on keeping the balance shaft but my crank shaft had to be re-machined, sorry if i was unclear about that. anyways, with all forged pistons and rods, new rings and bearings i should be ready to roll with a descent shot of N20 if i am not mistaken. I'll be searched on that topic once i have the money for that and i will PM some people about what to get. From what i have read so far NX is the way to go. I'm not sure how many miles your engine has to live after you load it with N20. A friend at a local shop estimated 50k miles if you use it frequently with a descent sized shot. Upgraded intake is a must.
 

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Yeah, this is an expensive operation but it is already finished on my car because for some reason my piston over-extended and started knocking lightly on my block and eventually it got harder and harder, ran itself low on oil, scored the piston walls, and with 98k miles on it, i'm not going to complain about replacing all of that so my car should be back togather by the weekend and i can test it out. i plan on keeping the balance shaft but my crank shaft had to be re-machined, sorry if i was unclear about that. anyways, with all forged pistons and rods, new rings and bearings i should be ready to roll with a descent shot of N20 if i am not mistaken. I'll be searched on that topic once i have the money for that and i will PM some people about what to get. From what i have read so far NX is the way to go. I'm not sure how many miles your engine has to live after you load it with N20. A friend at a local shop estimated 50k miles if you use it frequently with a descent sized shot. Upgraded intake is a must.
It all depends on how you use nitrous oxide. I've always been a fan of the controllers that Jacobs Electronics makes...they allow the delivery to be dialed in across multiple RPM increments, so you start out with a very small shot (say 25hp...which also helps to avoid wheel-spin), then up a little more (say to 50hp), and full delivery above your specified RPM...using it in this fashion, instead of a sudden blast of say a 75hp shot is much easier on the engine and a more efficient use of the nitrous as well...:bigthumb:
 

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considering they weigh like what 10 lb together, i'd say no more than 4hp
 

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Discussion Starter · #18 ·
Either way i did not plan on removing the balance shaft, however, what i have learned so far is valuable. Some of the information deposited in this thread seems to be questionable, but again all HP gains are.
 

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:lol: balance shaft removal frees up 15whp? Damn that's something new. Especially for a car with a wopping 100whp stock
The SOHC 4G64 probably doesn't get 15hp but the 4G63T does. I've never had to do a bs delete on a 4G64 so...
 

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the stubby shaft doesn't wobble atleast not on the 4g6x motors the stubby shaft that you need to use is a balanced piece that comes stock on th 1.6l mirage

there are 2 different types of stubby shaft the is a non OEM part that doesnt have the oil passage in the middle but the OEM mistu part does

i took this picture of the 2 side by side


This is the shaft installed on the gear that has the sprocket on the other side


when you put the rear part of the case back on the stubby shaft is completely secure there is no wobbling at all if your front case is in good shape because the bigger section of the shaft fits snug inside of the rear case of the oil pump like this
 
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